In a printing field in recent years, the following methods have become to be adopted (instead of a method wherein a printing plate is mounted together with positioning onto a plate cylinder): a method wherein a printing plate is mounted onto a cylindrical support and put onto a plate cylinder; and a method wherein a cylindrical printing original plate is prepared by forming a pattern-formable resin layer on a cylindrical support and then a pattern is engraved on a surface thereof followed by putting onto a plate cylinder. In a printing method using such a cylindrical printing plate, time required for setup and for job change is short and a high-speed printing is possible whereby it has been receiving much attention.
In a cylindrical relief printing plate, a laser engraving method has become to be used in recent years. In the laser engraving method, laser beam is irradiated to a resin layer so as to decompose and remove the resin whereby an uneven pattern is formed on a surface of the printing plate. The laser engraving method is highly efficient because it is possible to process the steps from imaging to pattern formation on a cylinder. As to a material for the resin layer to be applied to the laser engraving method, there have been used a vulcanized rubber, a cured photosensitive resin produced by photo-curing of a photosensitive resin composition and a cured thermosetting resin produced by thermosetting of a thermosetting resin composition. There have been particularly many proposals for a method for producing a cylindrical printing original plate using a liquid photosensitive resin and a sheet-form photosensitive resin plate which have been widely used in the printing field.
The Patent Document 1 discloses a method for producing a seamless and continuous printing element by mounting a sheet-form printing original plate layer around a sleeve for printing and by bonding terminal areas thereof by means of dissolution or melting.
The Patent Document 2 discloses a method for producing a cylindrical printing original plate wherein a printing original plate layer sheet is mounted around a cylindrical support and an overlapped area of a starting terminal of the mounting and an ending terminal of the mounting is bonded by heating the overlapped area at 80° C. to 250° C. together with applying pressure thereto.
In the methods for producing a cylindrical printing original plate as being disclosed in Patent Documents 1 and 2, a cylindrical printing original plate is produced by bonding terminal areas of a sheet-form printing original plate by dissolving or melting them at high temperature. Accordingly, the production methods as such involve a thermochemical change of a printing original plate composition during the dissolution or melting process. In the cylindrical printing original plate produced as such, the bonded terminals are thermally deteriorated and joint strength between the starting terminal of the mounting and the ending terminal of the mounting is weak. Accordingly, when a laser engraving is applied thereto and a pattern is formed together with a high-speed revolution of the cylindrical printing original plate, the printing original plate is sometimes demounted from the support because of breaking of jointed area. In addition, there is also a problem in terms of production efficiency that toxic smell is generated due to evaporation of low-molecular ingredients of the printing original plate composition during bonding or that a stabilizing step such as cooling is necessary after the bonding.